Cup and method for making cup with integrally formed u-shaped bottom channel

ABSTRACT

The present invention provides a cup less likely to leak by forming a u-shaped channel about a periphery of a bottom blank, forming a top blank into a generally cylindrical shape, and coupling an edge of the top blank to the u-shaped channel of the bottom blank.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to the field of leakproof papercups and the making thereof.

[0002] Volume production of paper cups and plastic coated paper cups hasachieved considerable success in the United States of America andabroad. One deficiency inherent in the cups formed using a layer ofinsulating foam is that the leak rate per million cups is almost doublewhen compared to cups formed using plain paper stock. However,insulating foam cups have proven to be very popular. An unsolved problemis how to produce a better bottom seam seal for insulating foam cupssince most of the leaks occur where the side seam adjoining a lowercylindrical portion of the cup attaches to the bottom blank.

[0003]FIG. 1A shows a cross section of a prior art cylindrical cup 100.The peripheral wall 150 of cup 100 has its lower edge 160 curvedinwardly and upwardly forming a channel.

[0004] The circular bottom blank 110 is typically a single layer ofboard and has a downwardly extending skirt 120 formed about itsperiphery.

[0005]FIG. 1A also shows where the prior art applies heat to seal thebottom blank 110 to the peripheral wall 150. Heat is applied at 130 tothe interior of the shallow hollow formed below the ascending sidewall140 and the bottom blank 110.

[0006]FIG. 1B shows a more detailed cutaway of an X-point 180 where fivelayers of board come together. The X-point 180 is especially prone toleaks.

[0007] Typically, a single layer of board is shaped to form a peripheralwall 150 of a cup 100. The two edges of the peripheral wall board meetand overlap to form a side seam 170. The side seam 170 is created byoverlapping the two edges of the board and sealing them together.Because the board is overlapped to form the side seam 170, the side seam170 is two layers thick. Because the peripheral wall 150 has its loweredge 160 curved inwardly and upwardly to form the channel, a doublelayer of the peripheral wall 150 is thus also curved inwardly andupwardly at the seam 170.

[0008] At all points where the peripheral wall 150 meets the bottomblank 110, except at the X-point 180, there are three layers of board.To seal the peripheral wall 150 to the bottom blank 110, the heat mustpenetrate two layers of board. The two layers of board are theperipheral wall's 150 single layer and the bottom blank's 110 singlelayer.

[0009] But, at the X-point 180 is where side seam 170 meets theperiphery of bottom blank 110, the side seam 170 is four layers thick,two layers on the outside and two layers on the inside where the sideseam 170 is folded upward. When the bottom blank 110 is then coupled tothe top blank, the X-point 180 becomes five layers thick. To seal at theX-point 180, the heat must penetrate three layers of board. The threelayers of board are the side seam's 170 two outer layers and the bottomblank's 110 single layer.

BRIEF SUMMARY OF THE INVENTION

[0010] The present invention provides a cup less likely to leak byforming a u-shaped channel about a periphery of a bottom blank, forminga top blank into a generally cylindrical shape, and coupling an edge ofthe top blank to the u-shaped channel of the bottom blank.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The above and other features and advantages of the invention willbe more apparent from the following detailed description wherein:

[0012]FIG. 1A (Prior Art) is a cross sectional, elevational view of aconventional paper cup viewed at a side seam showing the X-point whichis prone to leaking;

[0013]FIG. 1B (Prior Art) is a cross sectional, elevational view of aprior art cup showing the X-point being five layers thick;

[0014]FIG. 2A is a cross sectional, elevational view of a bottom blankof one embodiment of this invention having a first bend forming acircular flange;

[0015]FIG. 2B is a cutaway of a bottom blank of one embodiment of thisinvention having a fully formed u-shaped channel;

[0016]FIG. 3 is a plan view of a bottom blank of one embodiment of thisinvention with scores making it easier to form part of the bottom blankinto a u-shaped channel;

[0017]FIG. 4 is a schematic showing the placement of the polyethylenecoatings;

[0018]FIG. 5 is a cross sectional, elevational view showing where heatis applied to fuse the polyethylene coatings to their surfaces;

[0019]FIG. 6 is a cross sectional, elevational view of a top blankcoupled to a bottom blank in a u-shaped channel;

[0020]FIG. 7 is a cross sectional, elevation view showing where heat isapplied to join a top blank and a bottom blank together;

[0021]FIG. 8 is a perspective view showing how a top blank and a bottomblank are coupled in a u-shaped channel; and

[0022]FIG. 9 is a cutaway perspective view of a side seam and X-point ofa cup.

DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention comprises an improved cup where the bottomperiphery of a generally cylindrical top blank without a lower channelfits into a bottom blank having a preformed, generally u-shaped channelabout its periphery.

[0024]FIG. 2A shows a bottom blank 200 having an upper surface 220. Thebottom blank 200 has a first bend 210 and a second bend 240 to create anedge 230 about the periphery of the bottom blank 200. FIG. 2B shows acompletely formed bottom blank 250 with the first bend 210 and thesecond bend 240. The second bend 240 is completed to form a u-shapedchannel 260 about the periphery of the bottom blank 250.

[0025]FIG. 3 is the bottom blank 250 in a plan view, with scoring 300 toassist with the forming of the bends 210, 240 shown in FIGS. 2A and 2B.

[0026]FIG. 4 shows the surfaces of the top and bottom blanks coated withpolyethylene. When forming a foam-generated cup as disclosed in thefollowing U.S. Pat. Nos. 5,766,709, 5,840,139, 5,993,705, 6,030,476,6,129,653, 6,139,665, 6,142,331, 6,308,883, 6,319,590, and 6,328,557,the entire disclosures of which are incorporated herein by reference,the top blank 310 is coated on an inner surface 320 with polyethylene,preferably a blend of high density polyethylene (HDPE) and low densitypolyethylene (LDPE). The blend of HDPE and LDPE is used because it formsa better seal and bond under heat with the LDPE on an inside part 400 ofthe u-shaped channel 260 as well as with the outer surface 330 whereside seam 800, as shown in FIGS. 8 and 9, is formed. When formingnon-foam-generated cups the inner surface of the top blank is commonlycoated with LDPE.

[0027] An upper surface 220 of the bottom blank 250 and an outer surface330 of the top blank 310 are coated with polyethylene, preferably a lowdensity polyethylene (LDPE). The coating is applied before any bendingand therefore lines the u-shaped channel 260.

[0028]FIGS. 5 and 6 show how the top blank 310 and the bottom blank 250are joined together so a bottom edge 510 of the top blank 310 fitswithin the u-shaped channel 260 of the bottom blank 250. FIG. 5 furthershows different methods of heat application prior to joining the topblank 310 to the bottom blank 250. Both methods fuse the polyethylenecoating on the top blank 310 to the bottom blank 250. First, heat can beapplied at 520, the outer 330 surface of the top blank 310, and at 500,the inner 320 surface of the top blank 310. Second, heat can be appliedat 530, the inside of the u-shaped channel 260. FIG. 6 shows a bottomedge 510 of the top blank 310 fitting into the u-shaped channel 260 ofthe bottom blank 250 after either method of heat application.

[0029]FIG. 7 shows two more methods of heat application that occur afterjoining the top blank 310 to the bottom blank 250. First, heat can beapplied at 730, an outer portion of the exterior of the u-shaped channel260.

[0030] Second, heat can be applied at 700, an inner portion of theexterior of the u-shaped channel 260. To reach the first joining layerof polyethylenes 710, the heat at 700 need only penetrate one layer ofboard. However, to reach the second joining layer 720 of polyethylenesthe heat at 700 needs to penetrate two layers of board. At the X-point600, the heat at 700 needs to penetrate three layers of board to reachthe second joining layer 720 of polyethylenes.

[0031] Both seals bond polyethylene to polyethylene creating a strongerbond.

[0032]FIG. 8 is an exploded perspective showing schematically how thetop blank 310 lines up with the bottom blank 250 and how the bottom edge510 of the top blank 310 fits into the u-shaped channel 260. FIG. 8further shows a side seam 800 along the top blank 310.

[0033] Prior art cups are manufactured by forming a frustral conicaltop, wrapping a bottom blank around a lower outer portion of the top,and curling the edges of the bottom blank inwardly.

[0034] Unlike the prior art where a bottom edge of the top blank isfolded inwardly and upwardly (See FIG. 1A), the present invention doesnot fold the bottom edge 510 of the top blank 310 (See FIG. 8).Therefore, there is one layer of board around the entire top blank 310except at the side seam 800 where there are two layers of board joinedto form the side seam 800.

[0035] An embodiment of the present invention is constructed by forminga bottom blank 250 into a frustral conical shape (See FIG. 2A), thenwrapping a top blank 310 around the bottom blank 250 so that the bottomedge 510 of the top blank 310 fits into what will become the u-shapedchannel 260 (See FIG. 5). Next, the outer edge of the bottom blank 250is curled around the bottom edge 510 of the top blank 310 forming theu-shaped channel 260 (See FIG. 6).

[0036]FIG. 9 shows a cross-sectional cutaway of a completely formed cup900 having a side seam 800 two layers thick. The X-point 600 is 4 layersthick.

[0037] The side seam's 800 two layers 910, 920 are shown within theu-shaped channel's two layers 930, 940 making the X-point 600 fourlayers thick. Having an X-point only four layers thick is a reduction byone layer of board over the prior art. This reduction in the number ofboard layers at the X-point aids in the final joining process anddiscloses a cup less likely to leak.

[0038] While certain exemplary embodiments have been described in detailit is to be understood that such embodiments are merely illustrative ofand not restrictive on the broad invention, and that this invention isnot to be limited to the specific arrangements and constructions shownand described, since various other modifications may occur to those withordinary skill in the art.

What is claimed is:
 1. A method for constructing an improved bottom sealfor cups, the method comprising the steps of: forming a u-shaped channelabout the periphery of a bottom blank; forming a top blank into agenerally cylindrical shape; and coupling one edge of the top blank tothe u-shaped channel of the bottom blank.
 2. The method of claim 1,further comprising the step of: coating an upper surface of the bottomblank with polyethylene.
 3. The method of claim 2, further comprisingthe step of: coating an inner surface of the top blank withpolyethylene.
 4. The method of claim 3, further comprising the step of:coating an outer surface of the top blank with polyethylene.
 5. Themethod of claim 4, further comprising the step of: applying heat insidethe u-shaped channel prior to coupling the top blank to the bottomblank.
 6. The method of claim 4, further comprising the step of:applying heat to the top blank prior to coupling the top blank to thebottom blank.
 7. The method of claim 6, wherein the heat is applied tothe inner surface of the top blank.
 8. The method of claim 6, whereinthe heat is applied to the outer surface of the top blank.
 9. The methodof claim 4, further comprising the step of: applying heat to an innerportion of an exterior of the u-shaped channel after coupling the topblank to the bottom blank.
 10. The method of claim 4, further comprisingthe step of: applying heat to an outer portion of an exterior of theu-shaped channel after coupling the top blank to the bottom blank 11.The method of claim 2, further comprising the step of: utilizing a lowdensity polyethylene for the polyethylene coating on the upper surfaceof the bottom blank.
 12. The method of claim 3, further comprising thestep of: utilizing a blend of low density polyethylene and high densitypolyethylene for the polyethylene coating on the inner surface of thetop blank.
 13. The method of claim 4, further comprising the step of:utilizing a low density polyethylene for the polyethylene coating on theouter surface of the top blank.
 14. The method of claim 3, furthercomprising the step of: utilizing a low density polyethylene for thepolyethylene coating on the inner surface of the top blank.
 15. Themethod of claim 1, wherein an X-point has four layers of board.
 16. Acup with an improved bottom seal for cups, the cup comprising: a bottomblank having a u-shaped channel about a periphery of the bottom blank;and a top blank, wherein one edge of the top blank is coupled to theu-shaped channel.
 17. The cup of claim 16, wherein an upper surface ofthe bottom blank is coated with polyethylene.
 18. The cup of claim 16,wherein an inner surface of the top blank is coated with polyethylene.19. The cup of claim 16, wherein an outer surface of the top blank iscoated with polyethylene.
 20. The cup of claim 17, wherein the uppersurface of the bottom blank is coated with a low density polyethylene.21. The cup of claim 18, wherein the inner surface of the top blank iscoated with a blend of low density polyethylene and high densitypolyethylene.
 22. The cup of claim 18, wherein the inner surface of thetop blank is coated with low density polyethylene.
 23. The cup of claim19, wherein the outer surface of the top blank is coated with a lowdensity polyethylene.
 24. The cup of claim 16, wherein heat is appliedto the top blank prior to coupling the top blank to the bottom blank.25. The cup of claim 24, wherein the heat is applied to the innersurface of the top blank.
 26. The cup of claim 24, wherein the heat isapplied to the outer surface of the top blank.
 27. The cup of claim 16,wherein heat is applied inside the u-shaped channel prior to couplingthe top blank to the bottom blank.
 28. The cup of claim 16, wherein heatis applied to an inner portion of an exterior of the u-shaped channelafter coupling the top blank to the bottom blank.
 29. The cup of claim16, wherein heat is applied to an outer portion of an exterior of theu-shaped channel after coupling the top blank to the bottom blank. 30.The cup of claim 16, wherein an X-point has four layers of board. 31.The method of claim 4, wherein the low density polyethylene is foamable.32. The method of claim 1, wherein the top blank is constructed fromfoamable material.
 33. The method of claim 1, wherein the bottom blankis constructed from foamable material.
 34. The cup of claim 16, whereinthe top blank is constructed from foamable material.
 35. The cup ofclaim 16, wherein the bottom blank is constructed from foamablematerial.
 36. The method of claim 1, wherein the top blank isconstructed from stock comprising a base layer, an insulating layerapplied to at least one surface of the base layer and an expansionlimiting layer applied to at least a portion of the insulating layeropposed to the base layer.
 37. The method of claim 1, wherein the bottomblank is constructed from stock comprising a base layer, an insulatinglayer applied to at least one surface of the base layer and an expansionlimiting layer applied to at least a portion of the insulating layeropposed to the base layer.
 38. The cup of claim 16, wherein the topblank is constructed from stock comprising a base layer, an insulatinglayer applied to at least one surface of the base layer and an expansionlimiting layer applied to at least a portion of the insulating layeropposed to the base layer.
 39. The cup of claim 16, wherein the bottomblank is constructed from stock comprising a base layer, an insulatinglayer applied to at least one surface of the base layer and an expansionlimiting layer applied to at least a portion of the insulating layeropposed to the base layer.
 40. The method of claim 1, further comprisingthe step of coating an inner surface of the top blank with a laminatesynthetic resin.
 41. The cup of claim 16, wherein an inner surface ofthe top blank is coated with a laminate synthetic resin.
 42. The methodof claim 1, further comprising the step of coating an outer surface ofthe top blank with a foamable synthetic resin.
 43. The cup of claim 16,wherein an outer surface of the top blank is coated with a foamablesynthetic resin.
 44. The method of claim 1, further comprising the stepof coating a surface of the top blank with a thermoplastic syntheticresin.
 45. The method of claim 1, further comprising the step of coatinga surface of the bottom blank with a thermoplastic synthetic resin. 46.The method of claim 44 or 45, further comprising the step of applyingheat to the coated surface.
 47. The cup of claim 16, wherein a surfaceof the top blank is coated with a thermoplastic synthetic resin.
 48. Thecup of claim 16, wherein a surface of the bottom blank is coated with athermoplastic synthetic resin.
 49. The cup of claim 47 or 48, whereinheat is applied to the coated surface.